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Thread: Square thread rod
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15th Feb 2018, 10:35 AM #1Senior Member
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- Jul 2010
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- Brisbane
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Square thread rod
Hi... Looking for a supplier of square thread rod for a project i am working on.. 11/16 dia...6 tpi.
Was considering making it on a lathe, but apparently is more difficult that it seems..
Ken.
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15th Feb 2018, 02:30 PM #2Senior Member
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- Sep 2007
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- Country West Oz
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Depending on how long you need, it shouldn't be too bad to make on the lathe.
Regards
Bradford
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23rd Feb 2018, 11:19 AM #3Member
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- Oct 2017
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- Lismore, NSW
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- 58
G'Day Ken,
Some info that may help you with the square thread.
Sq Tooling005.jpg
The most important point of screw cutting a square thread is the correctly tool geometry. It may take a little practice to grind the HSS tool freehand but, it's not impossible.
Fig 1. shows the calcs required to find the lead/helix angle of the thread. This is then used to find the side clearance of the leading & trailing sides of the tool. To the calculated helix angle an additional 3˚ to 5˚ is added provide clearance between the thread flank & the tool on the leading edge. To the trailing edge of the tool, subtract 3˚ to 5˚ from the helix angle, Fig 2.
The width of the tool should should cut the thread groove slightly wider than the thread to provide working clearance (say 0.02mm min.)
Back clearance Fig 3, is also very important to stop any wedging effect due to interference as the depth of the groove increases.
I hone the tool width at the cutting edge to final size by measuring the tool width with a micrometer. Honing also gives small flats either side of the cutting edge that helps to improve the thread flank finish.
Tool back rake & front clearance are not shown on Fig 3, as these angles are dictated by the type of tool holder being used. Back rake 10˚ to 12˚, front clearance 5˚ to 10˚. No side rake is required.
Hope this is of some value.
Regards,
Don.
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